[ edit] data interface
according to different data interfaces, hard disks can be roughly divided into ATA and SATA (refer to IDE interface) and SCSI and SAS.
ATA, whose full name is Advanced Technology Attachment, uses the traditional 4-pin parallel data cable to connect the motherboard with the hard disk. The maximum external interface speed is 133MB/s, because the parallel cable has poor anti-interference performance and the cable takes up space, which is not conducive to computer heat dissipation, so it will be gradually replaced by SATA.
SATA, the full name of Serial ATA, which is the ATA interface using serial port, has been more and more accepted because of its strong anti-interference, much lower requirements for the length of data line than ATA, and support for hot plug and other functions. The external interface speed of SATA-I has reached 15MB/s, and SATA-II will rise to 3MB/s, so SATA has a bright future. The transmission line of SATA is much thinner than that of ATA, which is beneficial to the air circulation in the enclosure.
SCSI, the full name of which is Small Computer System Interface, has gone through many generations of development, from the early SCSI-II to the current Ultra32 SCSI and Fiber-Channel, and there are also many connector types. SCSI hard disk is widely used in workstation-class personal computers and servers, because it has a high speed, up to 15 rpm, and takes up less CPU computing resources during data transmission, but the unit price is also more expensive than ATA and SATA hard disks with the same capacity.
SAS(Serial Attached SCSI) is a new generation of SCSI technology. Like SATA hard disk, it adopts sequential technology to obtain higher transmission speed, which can reach 3 GB/s.. In addition, the internal space of the system is improved by narrowing the connecting line.
in addition, because SAS hard disks can share the same backplane as SATA hard disks * * *, in the same SAS storage system, some expensive SCSI hard disks can be replaced by SATA hard disks, saving the overall storage cost.
[ Edit] Power Interface
Molex logo at the power port of Seagate hard disk
The power cord of the internal hard disk of the computer is D-shaped 4-pin power connector, and the black is SATA power cord
5.25-inch and 3.5-inch desktop hard disks, using D-shaped 4-pin power connector (commonly known as big 4pin), which is designed and patented by Molex Company; Or SATA power cord.
The 2.5-inch hard disk for notebook computers can get power directly from the data port without additional power interface. After the external portable hard disk box is plugged in, the power source is provided by the USB interface outside the computer, and the power supply of a single USB port is about 4~5V 5mA. If the power demand in mobile hard disk box is high, it is sometimes necessary to connect two USB ports to use it, otherwise, an external power supply is needed. But nowadays, most new hard disk boxes (using hard disks below 2.5 inches) can conveniently use a single USB port to supply power.
[ edit] structure
[ edit] tracks
[ edit] cylinder
A cylinder composed of tracks with the same radius in a disk group composed of multiple disks.
[ Edit] Sector
[ Edit] Master Boot Record (MBR) Data Structure
[ Edit] 2.5-inch hard disks are mostly used in notebook computers
Comparison of the sizes of p>5.25-inch hard disks and 3.5-inch hard disks
The sizes and uses of hard disks can be divided into:
* .85 inches.
* 1 inch (MicroDrive), mostly used for digital cameras (CF type II interface).
* 1.8 inches, mostly used in notebook computers and external hard disk boxes.
* 2.5 inches, mostly used in notebook computers and external hard disk boxes.
* 3.5 inches, mostly used in desktops and external hard disk boxes.
* 5.25 inches, mostly used by early personal computers. There is no manufacturer to produce it today.
m = = main parameters ==
In addition to the interface and size, the hard disk has the following parameters:
Capacity At present, the capacity of the hard disk is 36GB, 64GB, 73GB, 8GB, 12GB, 15GB, 16GB, 2GB, 25GB, 32GB and 4GB.
the number of revolutions per minute of the rotating speed hard disk, in rpm (revolutions per minute), mainly includes several specifications such as 42rpm, 54rpm, 72rpm, 1rpm and 15rpm.
there are mainly 2MB, 8MB, 16MB and 32MB cache specifications.
the unit of average seek time is ms (millisecond), with specifications such as 5.2ms, 8.5ms, 8.9ms and 12ms.